Control channel architecture with control information distributed over multiple subframes on different carriers

ABSTRACT

Control information (126) related to the reception of data (128) within a subframe (116) is transmitted over multiple subframes (113, 116) over multiple carrier (107, 108) from communication system infrastructure (102). A controller (134) in a mobile wireless communication device (104) reconstructs the control information (126) received over multiple subframes (113, 116) based on at least some control information (130) in a first physical control channel (118) in a first subframe (113) transmitted over a first carrier (107) and at least some other control information (132) in a second physical control channel (120) in a second subframe (116) transmitted over a second carrier (108).

RELATED APPLICATIONS

The present application is a continuation of and claims priority to U.S.application Ser. No. 13/703,871, entitled “CONTROL CHANNEL ARCHITECTUREWITH CONTROL INFORMATION DISTRIBUTED OVER MULTIPLE SUBFRAMES ONDIFFERENT CARRIERS” and filed on Dec. 12, 2012; which is a nationalstage application of PCT/US2010/039175, entitled “CONTROL CHANNELARCHITECTURE WITH CONTROL INFORMATION DISTRIBUTED OVER MULTIPLESUBFRAMES ON DIFFERENT CARRIERS” and filed on Jun. 18, 2010; which isrelated to International Patent Application Serial NumberPCT/US2010/039185 entitled “CONTROL CHANNEL ARCHITECTURE WITH CONTROLINFORMATION DISTRIBUTED OVER MULTIPLE SUBFRAMES” and filed Jun. 18,2010; all of which are assigned to the assignee hereof and herebyexpressly incorporated by reference in their entirety.

BACKGROUND

The invention relates in general to wireless communication systems andmore specifically to control signals in a wireless communication system.

Base stations in cellular communication systems provide communicationsservices to wireless communication devices within geographical cellswhere each base station exchanges signals with wireless communicationdevices within an associated cell. The size and shape of each cell and,therefore, the coverage area of the base station are determined byseveral factors and are at least partially based on design parameters ofthe base station. In addition to large macro cells that provide servicesto numerous devices within relatively large geographical areas, somecellular communication systems are increasingly employing smaller cellsto increase efficiency, improve coverage, improve the quality ofservice, and provide additional services. The smaller cells may includea variety of sizes typically referred to as microcells, picocells andfemtocells. Microcells and picocells are often implemented within officebuildings, shopping centers and urban areas in order to provideadditional security, higher user capacity for the area, additionalservice features, and/or improved quality of service. Femtocells haverelatively smaller geographical areas and are typically implemented atresidences or small office locations. Since typical cellular backhaulresources may not be available in these locations, femtocells aresometimes connected to the cellular infrastructure through DSL or cablemodems. Femtocells are part of the cellular network and, therefore,communicate with the wireless devices using the same techniques as thoseused by macrocells. In addition to data information, control signals areexchanged between the base stations and mobile communication devices. Insome circumstances, control information is transmitted within a downlinkcontrol channel from a base station to a mobile communication where thecontrol information indicates how data communication can be receivedsuch as information on demodulation, decoding, etc. Communicationresources may be divided into frames including subframes. Inconventional systems, control information regarding the reception ofdata in a subframe is transmitted in the same subframe as the data.

SUMMARY

Control information related to the reception of data within a subframeis transmitted over multiple subframes over multiple carriers fromcommunication system infrastructure. A controller in a mobile wirelesscommunication device reconstructs the control information received overmultiple subframes based on at least some control information in a firstphysical control channel in a first subframe transmitted over a firstcarrier and at least some other control information in a second physicalcontrol channel in a second subframe transmitted over a second carrier.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block diagram of a communication system in accordance withan exemplary embodiment of the invention.

FIG. 1B is a block diagram of the communication system where the firstframe and the second frame are transmitted from a single base station.

FIG. 1C is a block diagram of the communication system where the firstframe is transmitted from a first base station and the second frame istransmitted from a second base station.

FIG. 2 is a graphical illustration of the first frame and the secondframe with a plurality of resource elements.

FIG. 3 is an illustration of a sub-frame in accordance with a 3GPP LongTerm Evolution (LTE) communication specification.

FIG. 4 is a flow chart of a method performed at the communication systeminfrastructure.

FIG. 5 is a flow chart of a method performed at a mobile wirelesscommunication device.

DETAILED DESCRIPTION

FIG. 1A is a block diagram of a communication system 100 in accordancewith an exemplary embodiment of the invention. The communication system100 may be implemented in accordance with any of numerous technologiesand communication standards. For the examples discussed below, thesystem 100 operates in accordance with an orthogonal frequency divisionmultiplex (OFDM) standard. The various functions and operations of theblocks described with reference to the communication system 100 may beimplemented in any number of devices, circuits, and/or elements as wellas with various forms of executable code such as software and firmware.Further, the reference to “first” and “second” components is made foridentification purposes and does not necessarily indicate any relativetiming information. For example, a second signal may be transmittedbefore, after, or at the same time as a first signal.

The system 100 includes communication system infrastructure 102 and atleast one wireless communication device 104. The communication systeminfrastructure 102 includes at least one base station but may includeseveral base stations and controllers connected through a backhaul. Inmost circumstances, several base stations are connected to a networkcontroller through network infrastructure to provide wirelesscommunication services to multiple wireless communication devices.

One or more wireless transceivers in the communication systeminfrastructure 102 exchange wireless signals 106 over at least twofrequency carriers 107, 108 with a wireless transceiver 110 in thewireless communication device 104. Accordingly, the communication systeminfrastructure 102 includes one or more transmitters for transmittingwireless signals to the wireless communication device 104 which includesa receiver for receiving the signals. Transmissions from thecommunication system infrastructure 102 and from the wirelesscommunication device 104 are governed by a communication specificationthat defines communication signaling, protocols, and parameters of thetransmission. The communication specification may provide strictspecifications for communication and may also provide generalrequirements where specific implementations may vary while stilladhering to the communication specification. Although the discussionbelow is directed to the 3GPP Long Term Evolution (LTE) communicationspecification, other communication specifications may be used in somecircumstances. The communication specification defines at least a datachannel and a control channel for uplink and downlink transmissions andspecifies at least some timing and frequency parameters for a physicaldownlink control channel from base stations to wireless communicationdevices. The control channel includes a broadcast control channel aswell as control channels scheduled to specific wireless communicationdevices. In an OFDM based system, a physical channel can be defined byallocating specific frequency-time resources. The granularity of theseresources depends on the specification and design of the system.

As discussed in further detail below, the transmission of frequency-timeresources, sometimes referred to as resource elements, is defined withinframes 111, 112. The frames 111, 112 are simultaneously transmitted overdifferent frequency carriers 107, 108. In FIG. 1, the second carrier 108and the frame 112 are represented with an arrow and box having heavierlines than the arrow and box representing the first carrier 107 andframe 111 in order to convey that the first frame 111 is transmittedover the first carrier 107 and the second frame 112 is transmitted overthe second carrier 108. The first frame 111 transmitted over the firstcarrier 107 includes several subframes 113, 114 and the second subframe112 includes several subframes 115, 116. Each subframe 113, 114, 115,116 includes a physical control channel 117, 118, 120, 123 and aphysical data channel 119, 122, 124, 125. The physical channels 117-125of the two frames 111, 112 are different channels since the physicalchannels 117-125 of the two frames 111, 112 are transmitted at differentfrequencies. Although a particular implementation may further specifyfrequency, timing, and coding parameters for each base station and/orwireless communication device, conventional systems transmit controlinformation and the related data for a wireless communication device 104only within the same subframe.

In the examples discussed herein, however, the control information 126related to data 128 in a subframe 116 is distributed over at least oneother subframe 113 transmitted over a different frequency carrier 107.In one example, at least a first portion 130 of the control information126 is transmitted over a first physical control channel 118 of a firstsubframe 113 in the first frame 111 transmitted over the first carrier107 and at least a second portion 132 of the control information 126 istransmitted over a second physical control channel 120 of a secondsubframe 116 of the second frame 112 transmitted over the secondfrequency carrier 108, where the control information 126 facilitatesreception of data 128 in the physical data channel 124 of the secondsubframe 116. The transceiver 110 in the wireless communication device104 receives the subframes 113, 116 and a controller 134 reconstructsthe control information 126 from at least some of the controlinformation 130 in the first subframe 113 and at least some of thecontrol information 132 in the second subframe 116. The controlinformation 126 is used by the receiver of the transceiver 110 toreceive the data 128 in the physical data channel 124 in the secondsubframe 116. Although the example discusses distributing the controlinformation 126 over only two subframes, the technique may also beapplied to more than two subframes. In some circumstances, the controlinformation 126 is transmitted over the physical control channels of oneor more subframes other than the subframe 116 including the data towhich the control information 126 corresponds. Also, the second portion132 of the control information may not be transmitted within the samesubframe 116 as the subframe used for transmitting the data 128. Forexample, the control information 126 may provide information regardingthe reception of data 135 in a subframe 114 other than the secondsubframe 116. For the example of FIG. 1, the data 135 is transmitted ina physical data channel 125 in a subframe in the first frame 111 and isillustrated with a dashed line box to indicate that the transmission ofthis data 135 is an alternative to transmitting the data 128 in thesecond subcarrier 116. Further, the first and second subframes may betransmitted simultaneously in some circumstances. Therefore, the controlinformation is distributed over different subframes transmitted overdifferent carriers and is received at the mobile communication devicewhich uses the control information to receive the data.

As discussed herein, therefore, control information 126 is the completecontrol information required to be received by the wirelesscommunication device 104 in order to receive the data 128 to which thecontrol information 126 corresponds. Before transmission, the controlinformation 126 may be coded, or otherwise processed, to reduce errors.Consequently, some redundancy of information may occur between subframesand/or within a subframe. In some circumstances, the wirelesscommunication device 104 may be capable of only accurately receivingsome of the control information transmitted within each subframe but iscapable of reconstructing all of the control information 126 required toreceive the data 128. The control information 126 may also be scrambledbefore or after being separated into the multiple portions.

A controller 136 in the communication system infrastructure 102separates the control information 126 into a first portion 130 and asecond portion 130 and assigns the portions to two or more subframesthat may be transmitted over different carriers 107, 108. The separationis typically performed as a mapping of error coded control informationacross the subframes after the control information is error coded. Themapping results in the first portion of the control information 130mapped to the first physical control channel 118 of the first subframe113 and the second portion of the control information 132 mapped to thesecond physical control channel 120 of the second subframe 116. Thesecond subframe 116 also includes the data 128 within the data channel124. The frame 112 having the control information distributed over thesubframes 114, 116 is transmitted to the wireless communication device104. Based on at least some of the received information of the two ormore portions of control information 130, 132, the controller 134 in thewireless communication device 104 reconstructs the control information126. The received and decoded control information is used to receive thedata 128.

As discussed herein, the control information 126 is information or datarelated to communication between the base station 102 and the wirelesscommunication device 104. The control information 126 is transmittedwithin control channels. Accordingly, although a control channel may bedefined across multiple subframes in conventional systems, the examplesherein discuss transmitting information over multiple subframes usingeither multiple control channels or a single control channel definedover multiple subframes.

Transmission of the multiple portions of the control information 126 maybe from a single base station or multiple base stations. As discussedbelow with reference to FIG. 1C, for example, the first portion 132 istransmitted from a first base station over the first carrier 107 and thesecond portion 132 is transmitted from the second base station over asecond carrier 108.

FIG. 1B is a block diagram of the communication system 100 where thecontrol information 126 is transmitted from a single base station 138.The base station 138 transmits the first portion of the controlinformation 130 in the first frame 111 over the first carrier 107 andthe second portion of the control information 132 in the second frame112 over the second carrier 108. The transmission of the first frame 111and the second frame 112 is synchronized. The base station 138 mayinclude multiple transmitters or may include a single transmittercapable of transmitting multiple carriers. The controller 136 thatseparates the control information 126 in the portions 130, 132 may be anetwork controller or a base station controller depending on theparticular implementation. A receiver 140 in the transceiver 110 of thewireless communication device 104 receives the multiple carriers 107,108. After any required demodulation, descrambling, and decoding, theportions of the control information are combined to reconstruct thecontrol information 126. The control information 126 is used by thereceiver 140 and controller 134 to receive the data 128. As describedabove, the data 128 is transmitted over the same carrier 108 andsubframe 116 as the second portion 132 of the control information. Insome circumstances, however, the data 128 may be transmitted over adifferent carrier and/or different subframe.

FIG. 1C is a block diagram of the communication system 100 where thecontrol information 126 is transmitted from two base stations 138, 142.The controller 136 that separates the control information 126 in theportions 130, 132 is a network controller in the example discussed withreference to FIG. 1C. The controller 136, however, may be a base stationcontroller in one of the base stations 138, 142 or may be distributedover multiple controllers. In such implementations, communicationchannels are established between the controllers and base stations toprovide adequate transfer of information. The receiver 140 in thetransceiver 110 of the wireless communication device 104 receives themultiple carriers 107, 108 from the two base stations 138, 142. Afterany required demodulation, descrambling, and decoding, the portions ofthe control information are combined to reconstruct the controlinformation 126. The control information 126 is used by the receiver 140and controller 134 to receive the data 128. As described above, the data128 is transmitted over the same carrier 108 and subframe 116 as thesecond portion 132 of the control information. In some circumstances,however, the data 128 may be transmitted over a different carrier and/ordifferent subframe or may be transmitted from a third base station (notshown).

FIG. 2 is a block diagram of the frames 111, 112 in a frequency-timegraph 200 showing frequency-time resource elements 201, 202. The graph200 in not necessarily drawn to scale and only provides an exemplaryvisual representation. Numerous other combinations of resource elementsmay be used to transmit the control information 126 and the data 132.

The first frame 111 includes a plurality of subframes including at leasta first subframe (K) 113 and a first frame second subframe (K+1) 114.The second frame 112 includes a plurality of subframes including atleast a second frame first subframe (K) 115 and a second subframe (K+1)114. The frequency carriers 107, 108 used for transmission are eachdivided into a plurality of subcarriers. Transmissions is also dividedin time to define a plurality of times slots where the time slots arefurther divided into symbol times. For LTE communication specifications,each time slot includes seven symbol times. The combination of symboltimes and subcarriers defines resource elements 201, 202 of the firstframe 111 and second frame 112, respectively. Accordingly, a symboltransmitted over a subcarrier is a resource element. Each portion ofcontrol information 130, 132 transmitted in a subframe is transmittedusing one or more resource elements. The resource elements used fortransmission of related information may or may not be contiguous. Forthe example of FIG. 2, the first portion of control information 130 istransmitted using first symbols 204 over a first subcarrier 206 andsecond symbols 208 over a second subcarrier 210 in the first subframe113. The second portion of the control information 132 is transmittedusing third symbols 212 over the second subcarrier 210 and a thirdsubcarrier 214 in the second subframe 116 of the second frame 112. Thedata 128 is transmitted using fourth symbols 216 over the secondsubcarrier 210 in the second subframe 116. As explained above, at leastsome of the control information in the first portion 130 and at leastsome of the control information of the second portion 132 are requiredto reconstruct the control information 126. For example, the controller134 in the wireless communication device 104 may be able to reconstructthe control information 126 from successful reception of only theinformation transmitted in the second subcarrier and third subcarrier.For such a situation, corruption of the first symbols 204 transmittedover the first subcarrier 206 would not hinder the wirelesscommunication device from receiving the control information 126 andconsequently accurately receiving the data 132.

FIG. 3 is an illustration of a subframe 300 in accordance with a 3GPPLTE communication specification. The subframe 300 includes two slots302, 304, where each slot includes seven symbol times 306. The symboltimes 0, 1 and 2 in the first slot 302 form the physical control channel117, 118, 120, 123 which is a Physical Downlink Control Channel (PDCCH)308. Pilot signals (or Reference Signals) 310 are injected at symboltimes 0 and 4. The subframe 300 includes a broadcast channel that is aPhysical Broadcast Channel (PBCH) 312 and spans portions of symbol times3 and 4 of the first slot 302 and portions of symbol times 0 and 1 ofthe second slot 304. The data channel 119, 122, 124, 125 is a PhysicalDownlink Shared Channel (PDSCH) 314 and is covered by the remainder ofsymbol times 3-6 of the first slot 302 and symbol times 1-6 of thesecond slot 304. The sub-frame 300 also includes a primarysynchronization channel (P-SCH) 316 and a secondary synchronizationchannel (S-SCH) 318.

In an example where the control information 126 is transmitted inaccordance with the 3GPP LTE communication specification, therefore, afirst portion of the control information 130 is transmitted withinsymbol time 1 and/or symbol time 2 within the first and secondsubframes. As described above, the resource elements may be contiguousor noncontiguous within a subframe. The data 128 transmitted in thesecond subframe is transmitted over symbol times 3, 4, 5, and/or 6 ofthe first slot 302 and/or symbol times 1, 2, 3, 5, and/or 6 of thesecond slot 304.

FIG. 4 is a flow chart of a method performed at the communication systeminfrastructure 102. Although the method may be performed using anycombination of code and/or hardware, the method is facilitated byexecuting code on the controller 136 in the exemplary embodiment.

At step 400, the control information is separated into portions andassigned to a plurality of subframes. The separation may includeprocessing, scrambling, coding and mapping in accordance with knowntechniques of downlink physical channel processing. For the example ofFIG. 4, step 400 includes processing the control information at step 402and mapping the control information to multiple subframes at step 404.Mapping may include, antenna ports processing (related to MIMO/SDMA),and resource element mapping within Frequency-Time space as well asother processing. The processing and mapping results in error coding ofthe control information and distribution of the control information 126over multiple subframes in subframes that are transmitted over differentcarriers. As discussed above, for example, a first portion 130 is mappedto a first physical control channel 118 of a first subframe 113 of thefirst frame 111 and a second portion 132 is mapped to a second physicalcontrol channel 120 of a second subframe 116 of a second frame, wherethe data 128 to which the control information 126 corresponds is withina physical data channel 124 of the second subframe 116. The processingmay also include scrambling of the control information 126 before and/orafter the control information 126 is divided into portions.

At step 406, the control information is transmitted over multiplesubframes over multiple carriers. Based on the mapping and processing,downlink OFDM signals 107, 108 are generated and transmitted from thecommunication system infrastructure 102 to the wireless communicationdevice 104. As discussed above, a frame 111 is transmitted within thesignal on the first carrier 107 and another frame 112 is transmittedwithin the signal on the second carrier 108, where each of the twoframes has a plurality of time-frequency resource elements arranged in aplurality of subframes. The subframes include at least the firstsubframe 113 and the second subframe 116. Accordingly, a first portionof the control information 130 is transmitted in a physical controlchannel in a first subframe 113 in a first frame 111 over a firstcarrier 107 and a second portion of the control information 132 istransmitted in a physical control channel in a second subframe 116 in asecond frame 112 over a second carrier 108.

At step 408, the data 128 is transmitted within the second subframe 116.Since the second portion 132 and the data 128 are transmitted within thesame subframe, step 406 and step 408 are performed simultaneously. Insome situations, the data 128 is transmitted over third carrier and/or athird subframe.

FIG. 5 is a flow chart of a method performed at the wirelesscommunication device 104. Although the method may be performed using anycombination of code and/or hardware, the method is facilitated byexecuting code on the controller 134 within the wireless communicationdevice 104 in the exemplary embodiment.

At step 502, the first portion of the control information 130 isreceived within the first subframe 113. The receiver within the wirelesscommunication device 110 receives the OFDM signal over the first carrier107 where the signals includes the first frame 111, the first subframe113 and the first portion of the control information 130.

At step 504, the second portion of the control information 132 isreceived within the second subframe 116. The receiver 140 receives OFDMsignal over the second carrier 108 where the signal includes the secondframe 112, the second subframe 116 and the second portion of the controlinformation 132. The signal is demodulated, decoded and otherwiseprocessed, to receive the first and second portions 130, 132 of thecontrol information 126. The first frame 111 and the second frame 112are synchronized and are simultaneously received.

At step 506, the control information 126 is reconstructed from at leastsome of the first portion 130 and at least some of the second portion132. The portions may require additional processing in somecircumstances in order to reconstruct the control information. Where thecontrol information has been error coded or scrambled across thesubframes, descrambling and error decoding is applied to the receivedportions to retrieve the control information. As discussed above, insome circumstances, the control information 126 is retrieved with onlysome of the information of the first portion 130 and some information ofthe second portion 132. If the control information 126 is scrambled, itis also descrambled by the receiver and/or the controller.

At step 508, the data 128 is received using the control information 126.The receiver and controller 134 apply the control information 126 toaccurately decode, demodulate, and otherwise process the data 128 in thesecond subframe 116.

Clearly, other embodiments and modifications of this invention willoccur readily to those of ordinary skill in the art in view of theseteachings. The above description is illustrative and not restrictive.This invention is to be limited only by the following claims, whichinclude all such embodiments and modifications when viewed inconjunction with the above specification and accompanying drawings. Thescope of the invention should, therefore, be determined not withreference to the above description, but instead should be determinedwith reference to the appended claims along with their full scope ofequivalents.

What is claimed is:
 1. A wireless communication device comprising: areceiver configured to receive a first subframe having a first physicalcontrol channel comprising first control information and a secondsubframe having a second physical control channel comprising secondcontrol information, wherein the first subframe and the second subframedo not overlap in a time direction, and both the first controlinformation and the second control information are associated with athird physical data channel comprising data; and a controller configuredto obtain the data from the third physical data channel, using at leastone of the first control information and the second control information.2. The wireless communication device of claim 1, wherein the thirdphysical data channel is transmitted on another subframe different fromthe first subframe.
 3. The wireless communication device of claim 1,wherein the receiver is further configured to receive the first subframeand the second subframe from a base station.
 4. A method for a wirelesscommunication device comprising: receiving a first subframe having afirst physical control channel comprising first control information anda second subframe having a second physical control channel comprisingsecond control information, wherein the first subframe and the secondsubframe do not overlap in a time direction, and both the first controlinformation and the second control information are associated with athird physical data channel comprising data; and obtaining the data fromthe third physical data channel, using at least one of the first controlinformation and the second control information.
 5. The method for awireless communication device of claim 4, wherein receiving the firstsubframe and the second subframe comprises receiving the first subframeand the second subframe from a base station.
 6. A base stationcomprising: a transmitter configured to transmit a first subframe havinga first physical control channel comprising first control informationand a second subframe having a second physical control channelcomprising second control information, wherein the first subframe andthe second subframe do not overlap in a time direction, both the firstcontrol information and the second control information are associatedwith a third physical data channel comprising data, and the data isobtained from the third physical data channel using at least one of thefirst control information and the second control information.